Precision pump



March 9, 1965 J. HRDINA 3,172,295

PRECISION PUMP Filed July 31, 1962 11 1n 3 so I m 5 .5;

JIIRI HRDINA United States Patent 3,172,295 PRECHSHUN FUR/E Jiri Hrdina, ?rague, (lzechoslovakia, assignor to Ceskoslovenska Alradernie Ved, Prague, Czechoslovakia, an

institution of Czechoslovakia Filed July 31, 1962, Ser. No. 213,664 Claims priority, application Czechoslovakia, Aug. 8, 1961, 4863/61 3 Claims. ((31. 74-53) My invention relates to precision pumps and more particularly to laboratory slide valve pumps used as dosimeters in chromatographic absorption analysis (chromatography) or the like.

The actuating mechanisms of known pumps of said type, though quite complicated do not assure a satisfactory and precise working. It is an object of my invention to avoid the defects and disadvantages of the known devices and to provide reliably and precisely working slide valve pumps which assure a high degree of proportioning even after a long and extensive usage. More particularly my new device provides an automatic compensation of any play between cooperating parts of the actuating means which may arise after long and heavy use; it attains a precision of 1% or better at deliveries of 200 to 500 microliters per hour.

The said and other objects of my invention will be more fully understood from the following specification when read with the accompanying drawing in which one embodiment is schematically illustrated in an elevational v1ew.

An oscillating driving shaft 1 carries a driving cam 2 and a distribution cam 3. The distribution cam 3 actuates a lever 3 which swings about journal 3" and supports and reciprocates in vertical direction the slide valve of a pump cylinder 11 wherein piston rod or plunger 11 reciprocates. The driving cam 2 cooperates with a roller 4 mounted on the end of one arm of a rocking knee lever 5 which swings about an adjustable fulcrum 6. The end of the other lever arm is jointedly connected by a pin 7 to one end of a push rod 8 which with its other end supports from below a cross pin 9 mounted in a head piece 10 of piston rod or plunger 11. The outer or lower face 12 of the head piece It is operatively located opposite a pin 13 mounted in one arm of another lever 14 swingable on journal 15, and it strikes in its lowermost position said pin 13. The end of the other arm of lever 14 is provided with a pin 16 which abuts against the head 17 of an adjusting screw 18 passing through a slit nut 19 tightenahle by a screw 20. The stem of the adjusting screw 18 is guided in a bearing 21 and is provided with an operating knob 24 and with a disk 22 which cooperates with a graduation 23 marked to indicate each full turn of the adjusting screw 18.

A pull rod 26 at one end partially embraces from above the said pin 9 and at its other end is linked by a pin 27 to one arm of a knee lever 28 which is swingably mounted on journal 29; the other arm of said lever 28 bears on springs 30 and 3% the force of which may be regulated and set by the screw 31 which passes through the stationary screw thread 32 and is secured by the lock nut 33. Thus the pull rod 26 is permanently drawn away from the pump cylinder 11 and the piston rod 11 outwardly thereof.

Locking means are provided to arrest the lever 28 with its horizontal arm in elevated position and thus to elirninate the action of the spring 3% upon the pin 9 and the members connected therewith. Said locking means comprise a dog 35 actuated by lever 36 and they are operated whenever it is desired to gain access to or to remove the pin 9 and to partially dismount the device for clearing or 3,172,295 Patented Mar. 9, 1965 "Ice other purposes. To prevent in such case an undesired outswinging of the rods 3 and 26 from their shown operative position, each of said rods is provided with a forked extension 39, 40, respectively, which is loosely engaged by a stationary peg 37, 38, respectively.

The journal forming the fulcrum 6 of lever 5 may be located in a plurality for example as shown in three positions to change the ratio of transmission between the cam 2 and the piston or plunger 11 and thereby regulate the stroke of the piston or plunger, said stroke being limited by the butt face 12 impacting the pin 13 of lever 14.

My new mechanism has the great advantage that it may be arranged and operated substantially within a plane containing the axis of the piston rod or plunger and that thus forces acting laterally upon the piston rod or plunger are avoided.

While one specific embodiment of my invention has been shown and described in detail to illustrate the application of the principles of my invention, it will be apparent to the expert that it may be otherwise embodied without departing from such principles.

I claim:

1. Mechanical movement means for the piston rod or plunger reciprocable in the cylinder of a precision pump particularly for laboratory use, comprising in combination (a) a cross pin associated with the outer end of the reciprocable piston rod;

(12) a push rod extending away from the cross pin substantially in the direction of the axis of the piston rod and associated with its neighboring end with the cross pin to push the piston rod into the pump cylinder;

(c) a pull rod extending away from the cross pin substantially in the direction of the axis of the piston rod and associated at its neighboring end with the cross pin to pull the piston rod out of the cylinder;

(d) adjustable stop means limiting the movement of the piston rod out of the cylinder and thus varying the sucking capacity of the pump;

(e) actuating means connected to the other end of the push rod to reciprocate the same in its longitudinal direction;

(f) and spring means acting upon the other end of the pull rod permanently urging the piston rod outwardly of the pump cylinder.

2. Mechanical movement means for the piston rod or plunger reciprocable in the cylinder of a precision pump particularly for laboratory use, comprising in combination (a) a cross pin associated with the outer end of the reciprocable piston rod;

(b) a push rod extending away from the cross pin substantially in the direction of the axis of the piston rod and leaning with its neighboring end with the cross pin to push the piston rod into the pump cylinder;

(0) a pull rod extending away from the cross pin substantially in the direction of the axis of the piston rod and leaning at its neighboring end against the cross pin to pull the piston rod out of the cylinder;

(d) adjustable stop means limiting the movement of the piston rod out of the cylinder and thus to vary the sucking capacity of the pump;

(e) actuating means connected to the other end of the push rod to reciprocate the same in its longitudinal direction;

(f) and spring means acting upon the other end of the pull rod permanently urging the piston rod outwardly of the pump cylinder.

3. Mechanical movement means for the piston rod or plunger reciprocable in the cylinder of a precision pump 3. particularly for laboratory use comprising in combination (a) a cross pin associated with the outer end of the reciprocable piston rod;

(b) a push rod extending away from the cross pin substantially in the direction of the axis of the piston rod and leaning with its neighboring end with the cross pin to push the piston rod into the pump cylinder;

(0) a pull rod extending away from the cross pin sub stantially in the direction of the axis of the piston rod and leaning at its neighboring end against the cross pin to pull the piston rod out of the cylinder;

(d) adjustable stop means limiting the movement of the piston rod out of the cylinder and thus to vary the sucking capacity of the pump;

(2) a double armed lever connected with one arm to the other end of the push rod to reciprocate the same References Cited by the Examiner UNITED STATES PATENTS 2,271,019 1/42 De Mattia 74-53 2,564,793 8/51 Seter 103-38 2,677,281 5/54 Gibson 74-53 FOREIGN PATENTS 555,235 3/23 France.

BROUGHTON G. DURHAM, Primary Examiner. 

1. MECHANICAL MOVEMENT MEANS FOR THE PISTON ROD OR PLUNGER RECIPROCABLE IN THE CYLINDER OF A PRECISION PUMP PARTICULARLY FOR LABORATORY USE, COMPRISING IN COMBINATION (A) A CROSS PIN ASSOCIATED WITH THE OUTER END OF THE RECIPROCABLE PISTON ROD; (B) A PUSH ROD EXTENDING AWAY FROM THE CROS PIN SUBSTANTIALLY IN THE DIRECTION OF THE AXIS OF THE PISTON ROD AND ASSOCIATED WITH ITS NEIGHBORING END WITH THE CROSS PIN TO PUSH THE PISTON ROD INTO THE PUMP CYLINDER; (C) A PULL ROD EXTENDING AWAY FROM THE CROSS PIN SUBSTANTIALLY IN THE DIRECTION OF THE AXIS OF THE PISTON ROD AND ASSOCIATED AT ITS NEIGHBORING END WITH THE CROSS PIN TO PULL THE PISTON ROD OUT OF THE CYLINDER; (D) ADJUSTABLE STOP MEANS LIMITING THE MOVEMENT OF THE PISTON ROD OUT OF THE CYLINDER AND THUS VARYING THE SUCKING CAPACITY OF THE PUMP; 